The abnormal visual pathways of albino mammals will be studied. Two approaches will be used: (1) The organization of the geniculocortical projection system will be studied to determine how the visual cortex deals with the abnormal input patterns. Anatomical studies will concentrate on mink, in which a variety of abnormal retinogeniculate projection patterns have already been defined. Also, we will use Siamese cats, in which the basic abnormality is well known, to determine how the geniculocortical system reacts to a unilateral lid suture. Anatomical studies of geniculate cell growth in such cats will be related to electro-physiological observations on cortical cells, and these results will be considered in the light of behavioral evaluations of the cats' visual abilities. (II) The development of the albino abnormality will be studied in several different species. The period during which pigment is laid down in the retina, the fetal fissure is closing and retinal ganglion cells are first sending axons into the optic chiasm will be studied by light and electron microscopical methods.